It is known that the saddles used in pedal vehicles, such as bicycles but also exercise bikes or wheel trainers for sports training, are formed by a shell made of a relatively rigid material, preferably covered by a relatively yielding padding layer that is intended to come into contact with the body of the user.
Generally, the shell comprises a rear portion intended to support the pelvis bones, in particular the ischial tuberosity and the surrounding muscular tissues, and a front portion intended to support the inguinal or scrotal zone of the user.
Typically, the rear portion is relatively enlarged and has a sufficient width for offering a relatively comfortable sitting, while the front zone must have a smaller width for allowing the user to extend the legs in a substantially vertical direction in order to carry out the pedal stroke.
One drawback of this saddle type is that the front portion of the saddle, even if tapered with respect to the rear portion, is in any case wide enough to oblige the user to rotate the knees outward, in order to avoid rubbing the thighs against the lateral edges of the saddle.
This phenomenon is even more evident when the users have very developed musculature and above all a thigh circumference that is relatively high with respect to the width of the pelvis. Comparative ergonomic studies conducted on different subjects have allowed verifying that users with a thigh circumference—pelvis width ratio above a certain value sustain rubbing between the inner thigh and the edge of the saddle, and a significant mechanical impediment to the correct extension of the thigh during the pedal stroke, in addition to high compressions of the adductor muscles.
From a functional standpoint, the user has a hard time completely extending the lower limb up to an approximately 145° angle with respect to the articulation of the knee and thus is obliged to rotate all of the articulations of the lower limb in an irregular manner, i.e. the femur, the knee and the ankle, proceeding with the classic pedal stroke with spread knees.
In order to avoid or reduce the aforesaid phenomena, users instinctively employ to different strategies: the first consisting of moving forward on the saddle, which can confer a greater pedal stroke freedom but also negative consequences for the comfort or the increase of perineal pain; the second consisting of lowering the saddle in a manner such that the leg does not extend in the final 10-15° of rotation, which bring the angle between the thigh and the leg from 130 to 145° extension.
In order to systematically study the phenomenon, a study was conducted on a sample of users of different size, weight and sex in order to obtain the value of the compression of the inner part of the thigh during the pedal stroke on the lateral edge of the saddle during the final 20° of movement before reaching the lower dead center. It was found that the pressure exerted in such zone can be quantified in 1 N/cm2, equal to about 10 kPa.
Assuming that this pressure is exerted on a surface area of about 4 cm2, it can be deemed that it determines an increase of the mechanical work, not useful for advancing, of about 70 Watt (about 1 Km/h from 39 to 40 km/h).
This increased mechanical work exerted by the muscles, which in this step are very contracted, alters the heart rate of the cyclist, increasing his physical overload. This situation can be compared to the case in which a car proceeds with the brake constantly on.
For a long time, there has been the need to obtain an ergonomic saddle structure that fully solves all these problems, decisively improving the functionality and the comfort for users at a very limited cost.
Saddles structures are known with a tapered front portion and an enlarged rear portion with convex edges, mutually joined by an intermediate portion with concave lateral edges, see for example US 2005/0017552, DE19901932 and U.S. Pat. No. 6,039,395.
However, these known saddle structures are mainly directed to improve the comfort in the ischiatic abutment zone and do not propose reducing the friction along the inner part of the thighs. Indeed, they have an intermediate connection portion between the front and rear portion which has lateral edges with excessive bend radius variation, on one hand limiting the abutment zone in proximity to the ischiatic bones and on the other hand exerting excessive friction until the movement of the thigh in the rear part of the saddle is blocked.
From FR 2451310, a connection device between the saddle and a seat post is known; such device has a predetermined width that is never associated with the minimum width of the saddle with which the device is connected.
US2006/0255631 discloses a saddle having all the features of the preamble of claim 1. However, this saddle has an enlarged rear portion substantially square-shaped which does not confer a comfortable stroke on the pedal.